“Rolls” and “cylinders” of the type under discussion here are usually, in their basic shape, cylindrical rotationally-symmetrical bodies which can be provided with a certain camber or a different specific shaping in order to be able to perform the respective rolling task in the respectively prescribed manner. In this respect, the “rolls” are generally directly coupled with the drive of the roll stand and are actively driven, whereas the “cylinders” are mounted in the roll stand without a direct drive and are only set into rotation during rolling operation due to the rolling contact with a roll or with the material to be rolled.
The problem being considered here arises equally in the case of rolls and cylinders, so that the following explanations apply equally to rolls and cylinders of a roll stand, even if only one of these components is mentioned.
The rolls and cylinders of roll stands are typically mounted in a respective mounting on rolling bearings in the region of their end journals. Said mounting can be formed in each case by a plurality of individual rolling bearings.
Due to the fact that the mountings on rolling bearings have to absorb considerable forces in rolling operation, high demands are imposed on their supply of lubricant. Thus, the respectively used lubricant serves on the one hand to reduce the friction arising in the rolling bearings. At the same time, the lubricant carries away some of the heat which forms in the respective bearing due to the rolling friction which is unavoidable there.
On account of this double function of the lubricant, considerable flows of oil are passed through the rolling bearings of a roll stand during practical rolling operation. This not only involves a costly oil supply for the apparatus, but large quantities of oil also have to be kept circulating, the preparation, stocking and disposal of which also entail a considerable complexity. In addition, in order to avoid leakage flows, extensive measures have to be taken to seal the bearings.
So-called “oil-air lubrications” have proved to be successful as an alternative to lubricating the rolling bearings of roll stands with considerable flows of oil. These oil-air lubrications allow a precisely metered allocation of the respectively required amount of lubricant to the respective lubrication points. The use of oil-air lubrication systems can not only drastically reduce the amount of lubricant kept in circulation, but also the risk of leaks forming and the necessary expense for sealing the bearings is significantly reduced compared to lubrication based on a conventional oil flow.
EP 0 902 868 B1 discloses an apparatus which is particularly suitable for use in roll stands and comparable machines for the uniform division of a lubricant-gas flow into a large number of discharge channels. This known apparatus comprises an inflow bore which branches into a large number of outflow lines. To achieve the uniform distribution, unaffected by gravitational influences, of the gas/lubricant flow while maintaining a turbulent flow in all outflow lines, the inflow bore opens into a distribution chamber which widens in the direction of flow. Configured in the transition region from the inflow bore to the distribution chamber is an encircling tear-of edge and on the wall of the distribution chamber opposite the end of the inflow bore is an impact surface which is aligned concentrically to the end opening of the inflow bore, the diameter of the impact surface being greater than the diameter of the inflow bore. Distributed around the periphery of the impact surface are the inlet openings of the outflow bores.
The assembly of the known apparatus in the bores of a roll stand is particularly simple in that the known distributing device has a tubular housing, on both end faces of which is formed a respective seat, the first seat of which is for receiving an inflow-side connection element and the second is for receiving a second connection element.
Prior apparatus for distributing a lubricant-gas flow are known from U.S. Pat. No. 5,253,733 or EP 0 010 269 B1.
In practice, compressed air is used in distributing devices of the type described above for advancing the respective lubricant and is usually provided in the surroundings of a roll train for rolling metallic strips.
By way of example, when there is only a small amount of space available in the region of the respective roll stand, the refit of already existing roll stands with oil-gas flow lubricating devices of the previously described type has proved to be problematic. Moreover, it is generally required in the case of new constructions that the outlay, required for the supply of lubricant to the rolling bearings, of supply lines and the like is reduced to a minimum, so that the maintenance of the bearing and repairs which may be necessary can easily be carried out.